This application is based on and incorporates herein by reference Japanese Patent Applications No. 2000-305228 filed on Oct. 4, 2000 and No. 2001-385791 filed on Dec. 19, 2001.
The present invention relates to a semiconductor device, in which heat is released from two sides of a semiconductor chip accommodated therein.
As that kind of device, a semiconductor device shown in FIG. 1 is proposed. As shown in FIG. 1, semiconductor chips 101, 102 and couplers 103, 113 are located between a first heat radiation plate 106 and a second heat radiation plate 105. Each semiconductor chips 101, 102 and corresponding coupler 103, 113, each semiconductor chips 101, 102 and the second heat radiation plate 105, and each coupler 103, 113 and the first heat radiation plate 106 are respectively electrically connected to each other by solders 104.
Therefore, the two semiconductor chips 101, 102 are electrically connected in parallel using the couplers 103, 113 and the first and second heat radiation plates 106, 105. Mold resin 109 is also located between the first and second heat radiation plates 106, 105 and in contact with a coating resin film 110, which is located on surfaces of the semiconductor chips 101, 102, the couplers 103, 113, and the first and second heat radiation plates 106, 105.
The semiconductor chips 101, 102 are respectively, for example, an IGBT chip 101, which is an insulated gate bipolar transistor, and an FWD chip 102, which is a fly-wheel diode. Each semiconductor chip. 101, 102 has an element formation surface 101a, 102a, or a front surface 101a, 102a and a back surface 101b, 102b, which is opposite to the front surface 101a, 102a. Each coupler 103, 113 is located on corresponding front surface 101a, 102a. 
The coupler 103 located on the front surface 101a of the IGBT chip 101 forms a space for wirebonding a bonding wire 108, which is described later, above the front surface 101a of the IGBT chip 101. The coupler 103 located on the front surface 102a of the FWD chip 102 adjusts the distance between the FWD chip 102 and the first heat radiation plate 106 such that the first heat radiation plate 106 becomes substantially parallel to the second heat radiation plate 105.
The second heat radiation plate 105 is electrically connected to the back surface 101b of the IGBT chip 101, which is a collector electrode, and the back surface 102b of the FWD chip 102, which is a cathode. The first heat radiation plate 106 is electrically connected to the front surface 101a of the IGBT chip 101, which is an emitter electrode, and the front surface 102a of the FWD chip 102, which is an anode.
The couplers 103, 113 and the first and second heat radiation plates 106, 105 release the heat that is generated by the semiconductor chips 101, 102 while functioning as electric wiring for the semiconductor chips 101, 102. Therefore, the solders 104 need to have a relatively high electric conductance and a relatively high thermal conductance.
Although not illustrated, a gate electrode is located at a predetermined position on the front surface 101a of the IGBT chip 101. The gate electrode is electrically connected to a control terminal 107 with the bonding wire 108. The semiconductor chips 101, 102, the couplers 103, 113, the first and second heat radiation plates 106, 105, the control terminal 307, and the bonding wire 108 are integrally molded with a molding resin used for forming the molding resin 109 such that a back surface 105b of the second heat radiation plate 105, a front surface 106b of the first heat radiation plate 106, and a portion of the control terminal 307 are exposed, as shown in FIG. 1.
Although not illustrated, cooling members, which cool the first and second heat radiation plates 106, 105, are located in contact with the back surface 105b of the second heat radiation plate 105 and the front surface 106a of the first heat radiation plate 106, so heat is efficiently released from the first and second heat radiation plates 106, 105.
In the semiconductor device shown in FIG. 1, the semiconductor chips 101, 102, the couplers 103, 113, and the heat radiation plates 106, 105 are respectively different in thermal expansion coefficient from the molding resin 109. Therefore, a relatively great stress is generated in the vicinity of the boundary between the molding resin 109 and each of the semiconductor chips 101, 102, the couplers 103, 113, and the heat radiation plates 106, 105 when the semiconductor device experiences thermal cycles. When the thermally generated stress overcomes the adhesion between the molding resin 109 and any of the semiconductor chips 101, 102, the couplers 103, 113, and the heat radiation plates 106, 105, the molding resin 109 peels off. The greater the difference in temperature of the thermal cycles, the smaller the number of the cycles that cause the peeling.
A stress is also generated in each solder 104 during the thermal cycles due to the difference in thermal expansion coefficient between the semiconductor chips 101, 102, the couplers 103, 113, and the heat radiation plates 106, 105. However, the stress in each solder 104 is suppressed by the molding resin 109 because the molding resin 109 restrains the thermal expansions of the semiconductor chips 101, 102, the couplers 103, 113, and the heat radiation plates 106, 105. Therefore, if the coating resin film 110 did not exist and the molding resin 109 peeled off any of the semiconductor chips 101, 102, the couplers 103, 113, and the heat radiation plates 106, 105, the stress in each solder 104 would increase and the solders 104 would deteriorate at an undesirably high rate. As a result, any solder 104 would crack, and the electric resistance of the solder 104 would increase.
The coating resin film 110 has a relatively high adhesion with the molding resin 109 and any of the semiconductor chips 101, 102, the couplers 103, 113, and the heat radiation plates 106, 105, so the molding resin 109 is prevented from peeling off during the thermal cycles.
Nevertheless, in the manufacturing process of the semiconductor device shown in FIG. 1, the solders 104 spread and adhere to any side surface of the semiconductor chips 101, 102 and the couplers 103, 113, as illustrated in FIG. 2. In that case, a portion of the solders 104, which is mechanically relatively weak, exists between the side surface and the coating resin film 110. If the semiconductor device having the portion of the solders 104 between the side surface and the coating resin film 110 experiences thermal cycles, the portion of the solders 104 peels off the side surface.
In other words, the molding resin 109 is disconnected from the side surface. In that case, as described above, the stress in that solder 104 increases and that solder 104 deteriorates at an undesirably high rate. In addition, in the case that two types of solders, which have a different melting point from each other, are used, the solders might be mixed with each other, and as a result, eutectic solder having a melting point much lower than those of the two types of solders might be formed to fuse at the temperature for the molding using the molding resin 109.
The present invention has been made in view of the above aspects with an object to provide a semiconductor device in which a molding resin is prevented from peeling off to assure the durablity in its electric performance.
In the present invention, a semiconductor device includes a first conductive member, a second conductive member, a semiconductor chip, which is located between the conductive members, a bonding member, which is located between the first conductive member and the semiconductor chip, and another bonding member, which is located between the second conductive member and the semiconductor chip.
The semiconductor device further includes a molding resin, which is located between the first and second conductive members to seal the semiconductor chip, and a bonding member anti-sticking means, which is located between the molding resin and a surface of one member selected from the group consisting of the semiconductor chip and the conductive members. The bonding member anti-sticking means prevents the bonding members from sticking to the surface in the manufacturing process. As a result, the otherwise insufficient connection due to the sticking between the molding resin and the surface is improved, and the semiconductor device becomes more durable in its electric performance.